The typical construction for a commercial or residential swimming pool uses a single pump. This pump causes circulation of water in the pool. It is a closed system in the sense that water is taken from the swimming pool thorough the skimmers by a suction created by a pump. The water pumped from the pool is passed through a filter or similar device for cleansing purposes. It may receive water treatment chemicals and then is returned to the pool from which the water was originally removed. Ordinarily, water is not added or lost during this process except small amounts that may be lost through leaks or evaporation. This system is an open hydraulic system in that the pressurized return water from the pump flows into an open body of water which is at atmospheric pressure. The filter pump is usually utilized to also provide suction to the skimmers. The skimmers are typically placed around the edge of a pool. Broadly speaking, a skimmer consists of a bucket-like device placed around the pool with an open side so that water from the pool can readily enter the skimmer bucket. There may be a check valve or weir door which will reduce wave action or other disturbances in the pool from taking floating material from the bucket once it has been pulled into the bucket by the suction created by the filter pump. At the bottom of the skimmer bucket is a pump suction inlet. Water is pulled through this suction inlet to the filter pump. Filters and pumps are normally sized at the pressure side of the pump and the pressure side performance always exceeds the suction pressure. The maximum suction pressure is limited by pump size, efficiency considerations, and atmospheric pressure.
This standard design results in a number of inefficiencies. First, there may be health department requirements regarding a minimum number of skimmers based on pool size. This may divide the return flow into the pump on the suction side into too many branches for efficient operation. Additionally, pools may be designed for aesthetic rather than pump efficiency purposes. Thus, landscaping and other esthetic design requirements determine routing of the return lines, which are not designed to equalize of maximize the efficiency of the return lines to the pump. If one or more of the skimmers are clogged by bad maintenance, or because of bad design, this may result in a higher suction at the remaining skimmers. This can result in poor cleaning of the pool or cause other health hazards like injury to pool users from high suction.